Conventionally, it is carried out to axially push a bearing race such that a gap in the interior of a bearing disappears, namely, to apply a preload to a rolling bearing. If the accuracy management of a bearing is difficult, or if there is a restriction due to the structure of a bearing housing around a bearing, a bearing race is axially pushed by a spring in some cases. As one of such bearing preloading devices, a bearing preloading device (as disclosed in Japanese Patent No. 4746469) is known in which at least one compression coil spring axially pushes a bearing race. Such a bearing preloading device is used, for example, for applying a preload to a double-row tapered roller bearing receiving a thrust load and supporting a work roller of a steel rolling machine.
In the case of an open-type bearing of which the interior is not filled with grease, as disclosed in Japanese Patent No. 4746469, drilled holes are formed in respective bearing races such that compression coil springs can be inserted into the respective drilled holes. In the case of a bearing in which grease is sealed inside of the bearing by oil seals provided separately from the bearing races and fixed to a housing, drilled holes are formed in annuli of the respective oil seals such that compression coil springs can be inserted into the respective drilled holes. In both cases, when the bearing is mounted, the compression coil springs are inserted into the respective drilled holes, and compressed to a predetermined extent, thereby generating an axial spring force. This spring force is applied to the bearing races.